1. Field of the Invention
The present invention relates to automatic control of engine speed in a fully or partially automated vehicular transmission system including an electronically controlled engine, preferably communicating over an electronic data link and allowing control in at least a speed-limiting mode and in a torque-limiting mode. In particular, the present invention relates to control of engine speed for such systems when a relatively large decrease in engine speed is required, typically when synchronizing for an upshift.
2. Description of the Prior Art
Fully and partially automated mechanical transmission systems intended for medium- and heavy-duty vehicular use are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,595,986; 4,648,290; 4,850,236; 5,582,558; 5,735,771; 5,755,639; 5,797,110; 5,894,758 and 5,904,635, the disclosures of which are incorporated herein by reference. Such systems typically involve some automatic control of engine speed to synchronize for engaging a target gear ratio.
The current fully or partially automated transmission systems may include an electronically controlled engine having control logic conforming to and/or communicating over an electronic data link conforming to an industry standard protocol, such as SAE J-1922, SAE J-1939, ISO 11898 or the like. U.S. Pat. Nos. 5,457,633 and 5,738,606 are illustrative of such electronically controlled internal combustion (usually diesel) engines.
Such systems have an engine speed mode of operation wherein the engine is controlled to achieve a target engine speed. In heavy-duty diesel engines, the engines are programmed to respond to engine speed mode commands by fueling the engine to achieve the target engine speed in a smooth, ramped manner.
The prior art systems are subject to improvement, as when commanding a relatively large decrease in engine speed in the speed control mode of operation, usually during a single or skip upshift, a longer-than-desirable time may be required to achieve the target engine speed.